Loan Amortization Calculator
Build a loan amortization schedule: payment, interest, principal, and remaining balance by period. Runs locally in your browser. Try it free.
Trust summary Engine tested · Specification checked · v1.1.0
- Input interpretation
- Enter values to calculate.
- Result
- —
- Model
- Payment, total interest, and a 12-period amortization summary.
- Scope
- Fixed rates and terms as entered; no fees or taxes unless modeled.
- Verification
- Engine tested · Specification checked · v1.1.0
- Named expert review
- Optional · Not performed
- Specification basis
- CFPB — amortizing loans: interest and principal portions of each payment
- Standard amortization schedule construction from the fixed PMT identity
Formulas
Core equations used by this calculator.
How to use
Enter the known values
Fill in each field with amounts and rates as labeled.
Calculate
Results update as you type; compare scenarios below when available.
Read the outputs
Check the result panel for the primary figure and supporting totals.
Example calculations
Common configurations with formula and result.
Worked example
250,000 · 6.5% · 30 yr → payment ≈ 1,580.17; first month interest ≈ 1,354.17
Loan Amortization calculator specification
Version 1.1.0 · Engine tested
- Engine tested 3 published cases
- Named expert review Not performed
- Calculation version 1.1.0
- Definition
- Amortization splits each payment into interest on the remaining balance and principal reduction. Early payments are interest-heavy; later payments are principal-heavy.
- What it calculates
- Payment, total interest, and a 12-period amortization summary.
- Inputs
- Values shown on the calculator form
- Outputs
- Primary result in the result panel
- Formula
Same PMT as loan payment; each period: interest = bal·r, principal = PMT − interest- Assumptions
- Fixed rates and terms as entered; no fees or taxes unless modeled.
- Calculation runs locally in the browser.
- Units
- Currency units as entered (dimensionless rates in %)
- Boundary conditions
- Zero or missing required fields yield zero or empty results.
- Negative inputs are treated as zero.
- Example
- 250,000 · 6.5% · 30 yr → payment ≈ 1,580.17; first month interest ≈ 1,354.17
- Validation cases
3 published on this page
- 250000 · 6.5% · 30 yr → payment ≈ 1580.17
- period 1 interest → ≈ 1354.17
- 0% rate → equal principal each month
- Specification basis
- CFPB — amortizing loans: interest and principal portions of each payment
- Standard amortization schedule construction from the fixed PMT identity
- Calculation version
- 1.1.0
Background
Interpretation and common distinctions.
About this calculator
Amortization splits each payment into interest on the remaining balance and principal reduction. Early payments are interest-heavy; later payments are principal-heavy.
Example
250,000 · 6.5% · 30 yr → payment ≈ 1,580.17; first month interest ≈ 1,354.17
Related tools
Other calculators in this family: Compound Interest, Simple Interest, ROI Calculator .
Frequently asked questions
Key distinctions behind the calculation.
How does the Loan Amortization Calculator work?
It uses Same PMT as loan payment; each period: interest = bal·r, principal = PMT − interest. All math runs locally in your browser.
Can I share my inputs?
Yes. Use Copy link in the result panel — the URL stores your current inputs.